.app{
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
}
.main{
    width: 100%;
    height: 100%;
    overflow: hidden;
    width: 100%;
}
.main *{
    box-sizing: border-box;
}
.main>*{
    float: left;
    height: 100%;
}
.main .nav{
    width: 200px;
    background-color: #545c64;
}
.main .content{
    border-left: 1px solid #e6eaee;
    width: calc(100% - 200px);
}